Answer:
- Attacked by the school bully,
- Slipping on the wet sidewalk,
Step-by-step explanation:
Dangling modifiers occur when the modifiers are far from the object they modify. As a result, the meaning of the sentence is confusing, obscure, ambiguous or senseless.
In the first sentence, it is unclear to deduce whether the backpack or Abner were attacked by the school bully. Thus, the right version could be:
The backpack fell from Abner's shoulder when he was attacked by the school bully.
In the third sentence, it is not precise to figure out whether Amaury or the keys were slipping on the wet sidewalk. As a result, the modifier should be placed closer to the modified object, as it stated in the second sentence:
When Amaury slipped on the wet sidewalk, the keys fell from his pocket.